--------------- Mon. Mar. 2 -------------
• 1) Class CEPHALOPODA, 3rd major class (nautilus, squids, octopus)

  • a) includes most highly advanced, largest & fastest invertebrates; body plan modified for pelagic life

  • b) exclusively marine carnivores (eat fish, crustaceans, molluscs)

  • c) shell is reduced or absent; head & foot form tentacles & siphon

  • d) 1 or 2 pair of ctenidia; have a true 'closed' circulatory system

  • e) mantle is muscular and mantle cavity large; jet-propulsion is achieved via antagonism of circular & radial mantle muscles

  • f) three subclasses (Nautiloidea, Ammonoidea-extinct, Coleoidea)
  --------------- Wed. Mar. 4 -------------

• 2) Class BIVALVIA, 2nd most diverse class (clams, oysters, scallops)cs

  • a) body plan modified for a burrowing, filter-feeding mode of life

  • b) body is laterally compressed & wholly enclosed inside mantle

  • c) shell composed of 2 valves joined by a flexible ligament; mantle edge is fused to the shell margin & linked to adductor muscles

  • d) foot highly modified for burrowing (except attached species); burrowing involves both shell and foot; head & radula are absent
    --------------- Fri. Mar. 6 -------------

  • e) 1 pair of ctenidia; may be small & mainly respiratory (protobranch) or large & modified for filter feeding (lamellibranch: may be either filibranch or eulamellibranch type)

  • f) most produce byssal threads as larvae, some still do as adults

  • g) classification still debated; 4 important subclasses (Palaeotaxodonta, Pteriomorphia, Heterodonta, Anomalodesmata)

• 3) Class SCAPHOPODA, the 'tusk shells'

  • a) curious tubular shell; originates as two shells in larva that fuse

  • b) head reduced, but have a well-developed foot for burrowing

  • c) lack ctenidia but possess a radula; capture forams with captacula

  ---

  --------------- Mon. Mar. 9 -------------
  PHYLUM SIPUNCULA (peanut worms)

• 1) Widespread phylum of approx. 300 species; marine deposit feeders

• 2) The bizarre body plan includes: 2 coeloms (small- tentacles, large- trunk), completely invertable head (introvert), crown of tentacles around mouth, unusual gut (terminal mouth, mid-dorsal anus)

• 3) Related to molluscs by: molluscan cross, eversible scraping buccal organ in larva, creeping muscular lip

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